1. Field of the Invention
The present invention relates to the heat treatment and the reheating of a charge in an industrial furnace and more particularly to a cooled tubular assembly comprising several sections offset relative to each other of different lengths to support said charge as it is moved through said industrial furnace.
1. Prior Art
Reheating furnaces are generally operated to increase the temperature of steel to a level at which the steel may be rolled. Immediately prior to rolling, temperature distribution across the material to be rolled should be as uniform as possible. However, in such a reheating furnace, the temperature of the charge is lower at the points at which said charge rests on water-cooled tubular supports--or on riders frequently placed between such tubular supports and said charge--than at unsupported points of the charge because charge heat-up by burners arranged below such tubular supports is impeded at the points at which said charge so rests on said supports and heat may be transferred from the charge to such water-cooled tubular supports. As the temperature of the charge must also be raised to rolling temperature at said points of supports, a soaking zone is provided for temperature equalization.
Heat transferred to slabs, billets and similar charges passes through the surface of the charge to the core which is heated more slowly. Temperature equalization is thence necessary in such a soaking zone which also ensures a more uniform temperature distribution avoiding relatively cold charge areas at the points where the charge rests on water-cooled tubular supports in the heat-up zone of such a furnace. There are several prior art approaches which seek to improve said temperature distribution.
West German Pat. No. 2 039 507 divulges a cooled tubular assembly comprising a tubular support crossing the furnace in a straight line in the direction of charge travel. Said tubular support is provided with riders arranged one after the other in one line on said support. Said riders are provided with charge-carrying surfaces which are either oblique relative to said tubular support or are arranged in an alternating manner to the left and to the right of the centerline of said tubular support. Said known arrangement of the charge-carrying surfaces of such riders ensures a more uniform heat flow from the charge to the cooled tubular support. However, temperature differentials in such a charge are determined by the position and the size of the entire tubular support with its riders relative to the position and the size of the charge being reheated and said relative position remains unchanged across the entire length of the furnace described in the above West German patent, thereby creating a relatively wide area of relatively low temperature in the charge entering the soaking zone of said furnace.
West German Pat. No. 31 15 930 also describes a reheating furnace provided with a tubular assembly. In the case of said furnace, the tubular supports across 10 to 30 per cent of the furnace length at the exit end of the furnace are jointly displaced laterally relative to the other tubular supports. The tubular supports so displaced are provided with riders. It is the object of the design known from said patent to cause the hot slabs moving directly on tubular supports in the heat-up zone to be carried by riders in the soaking zone of said furnace.